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H. M. PLAISTED. ROTARY HAMMER.

APPLICATION FILED DEC.l3.-19I9.

Reissued J uly 27, 1920.

INVENTOR. J2 Pia [6 2 ed v v MA rromv:

UNITED STATES PATENT OFFICE.

HAROLD M. PLAISTED, OF ST. LOUIQ, MISSOURI, ASSIGNOR F FORTY-NINE ONE-HUNDREDTHS TO WILLIAMS PATENT CRUSHER & PULVERIZER 00., OF ST. LOUIS,MISSOURI, A CORPORATION OF MISSOURI.

ROTARY HAMMER.

- Specification of Reissued Letters Patent. Reissued July 2'7, 1920.

Original No. 1,301,316, dated April 22, 1919, Serial No. 240,393, filedJune 17, 1918. Application for reissue filed- December 13, 1919. SerialNo. 344,710.

To all whom it may concern Be it known that I, HAROLD M. PLAIs'rEo, acitizen of the United States, residing at the city of St. Louis, Stateof Missouri, have invented certain new and useful Improvements in RotaryHammers, of which the following is a specification.

This invention relates to certain new and useful improvements in arotary hammer,

the peculiarities of which will be hereinafter described and claimed.

The main object of my invention is the pro vision of a rotary hammerhaving one or more wide operative edges and a shank of small relativethickness compared to its width set transversely to said edges, like aT, so as to present comparatively little surface-to the material beingreduced, and to provide means for avoiding interference between saidhammers.

In the accompanying drawing on which like reference letters indicatecorresponding parts,-

. Figure 1 represents a partial transverse sectional elevation of areducing machine embodying. my invention;

Fig. 2 a partial section- -o' he cage taken in an opposite direction,showing the preferred relation of my rotary hammers by an edge view oftheir" periphery;

Fig. 3 a detail face view of a shank hammer with its T-head;

Fig. 4 a similar side edge view of the shank and T-head; .and

Fig. 5 a top; view of the head shown in F i s. 3 and 4.

he letter A designates an arcuate cage of any suitable form concentricwith a shaft B on which are fastened hammer mounts, preferably consistinof disks C-C sup-,

of my porting hammer ro s D on which are piving said hammer.

' provided a cross There are preferably two of saidholes, the other holeE, being located the same distance on the opposite side of alongitudinal central line F through said shank, as is the center of saidhole, E.

At the other end of said shank there is piece extending laterallyoutward from each face of, said shank in opposite directions andsubstantially the same distance, so as to form a T-head. The lateralprojections forming said T-headextend outward substantially at rightangles to the flat faces of the shank; and are like wise of lesserthickness, measured radially through the pivot, than the width measuredin the plane of rotation. The narrow side dimension or radial edgethickness of these lateral projections forming the head is presented tothe material being reduced, similarly to the presentation of the sideedge of the flat bar shank. By forming a T-head and shank on myprinciple, none of the fiat side or width of the bar is presented to thematerial being reduced, but only the side-edge thickness, or lesserdimension of said bar. My hammer therefore tends to slice through thematerial being reduced; and likewise tends to avoid carrying around withthe hammer the material being operated on, as is the tendency with ahammer in which any of the flat side, or width of a flat bar ispresented toward the material being reduced. This cross piece ispreferably zigzag in plan view as shown in Fig. 5, and is preferablyformed, when of thiszigzag shape, by splitting the outer end of saidshank for a portion of the length along the longitudinal center line,and then forcing the respective halves of said end over in oppositedirections until they are substantially at right angles to each face ofsaid shank, and with each edge on the respective halves substantiallyequi-distant from the respective pivot hole center, measured diagonallyacross said central line F. In a quarter twist hammer the head and shankat the junction are not directly presenting the. lesser dimension of thebar to the material being reduced, but inevitably come this objection ina previous form of hammer in which the head and shank are connected by aquarter twist, that the present T-head is formed directly extendinglaterally outward on each side of the flat bar shank, substantially asshown. In this zigzag form of T-head in which the cross plate forms theT-head, the operative edges on each side of the shank are not directlyalined but are zigzag in the preferred form. The cross piece plate headmay be otherwise formed however. Four operative edges are thus formed onsaid cross piece,two edges on said sides of the shank G-G' being separated substantially the width of the shank, and the other two operativeedges being substantially in line with each other and traversingthecentral line F. In Fig. 3 full lines have been drawn from center of thehole E to the operative edges H and I at the side G, and the center lineF, respectively. These lines indicate that these operative edges aresubstantially equi-distant from the center of the hole E. The dashedlines in the same figure indicate that the operative edges J and Krespectively adjacent to the side G and the central line F are likewiseequi-distant from the center of the hole E.

This arrangement of the operative edges causes the cross piece formingthe T-head to assume the shape of two bevels as shown in Fig. 3. Theaction of a forging machine in forming hammers of this kind, willreadily swage the split end of the hammer into the shape desired so thatthe operative edges will be substantially as shown in the draw- 111g.

As will be seen by reference to Fig. 1, the forward operative edge H isin front of a radial line L from the shaft through the pivot center E,and the edge IK is a little behind said radial line,when said hammer isin its normal position under rotation. Thus said forward edges H and Iof the T- head are substantially the same distance from the cage A,while the rear edge J is a farther distance from said cage, due to thebevel-of said T-head and to the eccentric location of the pivot centerE. When said hammer is reversed and mounted on the pivot hole E theedges J and K come into similar operation.

The operative edges above described may be of any kind and shapedesired; that is, they may be sharp as shown in Fig. 1 throughout theirlength, or may be serrated with an under-cut saw-tooth shape as shown inFigs. '3, 4 and 5; or may be otherwise formed. When the front edges Hand I are of saw-tooth shape they are especially adapted to cuttingalfalfa and like material, and by their increased length of cutting edgefacilitate the cutting action and make the power required for rotatingthe hammers much less than other form of cutting opening in the adjacentdisk.

edge. Alfalfa mills however have a tendency to throw out the materialentering the mill, and I have therefore shown the edges J and K as plainor square edge in Fig. 3, and the edges H and I in the oppositedirection being formed with saw teeth. When a hammer of this design ismounted in disks as shown in Fig. 2,-that is, with the forward edges ofone hammer plain and the following hammer with the forward edgesserrated,-the action of the hammers is to to draw in as well as to cutthe alfalfa or like material.

While the forward edge of a hammer of my construction only presents thelesser dimension or edge thickness of the bar to the material being cutand allows the cutting edges to operate upon the material and passthrough said material with little obstructions, it is desirable toextend the cutting edge opposite the sides G and Gr so as not to losethe benefit of the thickness of the bar. This I do by means of a cut-outor notch M by which the bevel of the operative edge, H for instance, iscarried past and through 9 the thickness of the bar. In the use of asaw-tooth edge, this notch M would be sharpened, as shown at M, Figs. 3and 4, to avoid the alfalfa collecting on the side of the shank.

In a previous construction shown in Patent No. 1,281,829, dated October15, 1918, I

them broadly in connection with the opera- 1 tive edges there shown.

In Fig. 1 is shown a bearing edge P, and a bearing edge Q, locatedrespectively beyond, and inside, of the pivot of the hammer in itspocket S formed. b a cut-out hese edges in said pocket are adapted tocontact with the side G of said shank, and with a contact surface R- atthe inner end of said shank, respectively, and thus form stops for theoscillation of said hammer in both directions. It is es ially necessaryto limit the oscillation of ammers havin sharp ed s and prevent twohammers hittlng each ot er when one or both rebound, and thus dullingsaid edges. I avoid such interference b providing the bearing surfaces Pand located on the wall of the pocket as shown in this application. Itwill be noted that the bearing surface Q and the contact surface R, thatmeet when the hammer is on a rebound from the dotted position shown inpivot, but in a hammer of the construction shown in which the end thatis pivoted is substantially square, I have claimed the location and stopsurfaces as shown in this application.

It will be observed from the above that the hammer as an entirety whilesubstantially T-shaped has one cutting or reducing edge in advance ofthe other, but the speed at which these mills are usually 0 erated,establishes almost a condition 0 static equilibrium, so that there is notorsional strain on the shank of the hammer.

I claim:

1. A rotary hammer comprising a flat bar shank having two holes at oneend for pivotal mounting, saidholes being located on opposite sides of acentral longitudinal line, and a T-head on said shank having fouroperative edges extending transversely in opposite directions from thefaces of said shank, each pair of said edges being substantiallyequidistant from the center of,

the respective pivot holes, measured diagonally across the centrallongitudinal line.

2. A rotary hammer comprising a flat bar shank having a pivot hole atone end and a zigzag cross piece forming a T-head at the other end, saidhead having four operative edges, two of said edges being separated bysubstantially the width of said' shank, and the other two edges beingsubstantially alined with each other and extending in oppositedirections from the respective face of said shank.

3. A rotary hammer comprising a flat bar shank having a pivot hole nearone end, and provided with a T-head having a sawtooth cutting edgeadjacent to one side of said shank, and a lain ed eladjacent to theother side ofsaid s ank, substantially as and for the purpose described.

4. A rotary hammer comprising a flat bar shank, havin a pivot hole nearone end, and provided at the other end with a T-head having an operativecutting edge adjacent to one side of said shank, said shank beingsharpened for a portion of the side adjacent to said head, substantiallyas described.

5. Thecombination with a rotary pivot hammer having part of a sideradially beyond its pivot adapted for contact, and another part of thehammer radially inside of the pivot but on the opposite side of acentral line through said shank also adapted for contact, of a diskhaving a pocket for the pivot end of said hammer, said pocket havingbearing edges forming stops limiting the oscillation of said hammer andpre enting interference with adjacent hammers and located radiallybeyond said pivot, and radially inside of said pivot respectively but onopposite sides of a radial line from the shaft through said pivot,respectively, substantially as described.

6. A rotary hammer com rising a shank and a T-head, said T-head beingformed integral with the shank and having four operative edges.

7. A rotar hammer comprising a shank and a T-hea said T-head beingformed integral with the shank and each le of said lid-head havingoppositely disposed cutting e ges.

8. A rotary hammer comprising a shank and a T-head, said T-head beingrovided with oppositely disposed cuttin e ges, one of said edges beingplain and the other edge being serrated.

9. A hammer provided with a shank and a T-head having staggered serratedcutting edges and plain cutting edges oppositethereto, said shank beingprovided with openings on each side of the longitudinal axis of thehammer.

In testimony whereof, I hereunto aflix my signature, this 1st day ofDecember 1919.

HAROLD M PLAISTED.

